Pretty sure that's not the case here. To "turn down" is a common phrase (at least in the US) that is used to describe changing something by use of a control.
As described at Wiktionary [0] - it's an idiomatic way of saying that you're going to lower the volume through use of a control to do that. The context that was used has nothing to do with party.
[0] https://en.wiktionary.org/wiki/turn_down
EDIT: My bad, thought it was in response to...
> I guess it will mostly reflect the musical taste of assholes who turn their music up loud. Hmm, but maybe all culture works like that.
No, the above poster is talking about the Lil Jon song called "Turn down for what" and it's not about volume.
I bet you are just the type of square who thinks that U+1F346 represents an eggplant.
https://www.dictionary.com/e/slang/turn-down-for-what/
> At its core, turn down for what is a phrase used to promote having a good time. The phrase itself implies that there is no reason to turn down and stop partying.